When you're talking mufflers, what difference does a 3.5 or 4 inch muffler make on how the bike rides? I currently have stock mufflers (& headpipe) on a 2015 limited. Bike runs great, but quiet. I tried V&H Twin Slash Rounds on it and the bike ran bad parking lot speeds. Had to stay on the clutch and it bucked and bobbed a lot. Also noticed the throttle had a really small hesitation in it. Some guys might not even have notice it but I'm super picky, and did. The stock pipe looks smaller than the V&H. Is it the pipe size that caused the readability issues?

 

You need a tuner to run free flowing pipes. Your bike was running too lean. Usually you could run the slip ons but maybe you didn't give the ECU time to adjust. Do you have a stock air filter or a high-flow? High flow you definitely need a tuner

 

With a free-flow exhaust it is possible it was runnning rich, in any event the fuelling has been disturbed. Time for a suitable tuner!

 

I'm of the opinion that a free flow exhaust will cause a lean condition (when paired with a high flow intake) rather than a rich one. Either way, the OP will need to correct his tune.

 

Im running a catless header, 4" Freedom Performance Racing Slip-ons and a Power Vision tuner...Happy with both the sound and the increase in performance (according to the butt dyno).

Cams are in my future...

 

^^^Good feedback & agree^^^

If you didn't make any adjustments, after exhaust install, bike was running different which equals the issues you experienced. Adding a self-tuner really makes this problem easily corrected. On the newer bikes, Power Vision tuners are really popular and a good investment, if you plan to add more performance parts. Time to get it now, or put on your upcoming holiday wishlist.

http://www.dynojet.com/powervision/

 

I held the same view, however after changing the exhaust on my Buell, my local indy assured me that the banging on the over-run is unburned fuel in the exhaust, due to my aftermarket free-flow system. I share that for what it is worth. In any event a tuner has (almost) solved it!

 

Cheers!

 

3.5 vs 4" is not the concern- it is the internal flow-

this goes to the basics of exhaust system design.

most header pipes are 1.75" diameter- many mufflers have a 2" core, but there may be other sizes.
a larger muffler core ( remember internal size not external size) will cause the exhaust gasses to slow in the tract- this will affect how the following 4 cycles work in the motor:

IF the exhaust gasses move quickly, they form a low pressure zone behind them- this will suck or pull in fresh air on the next intake stroke...it is possible to get a more than 100% cylinder fill- which will make more power
( the cylinder is 844CC- tuning can perhaps get 900cc of air in there)

with a stock type header ( or 2/1) where the headers connect, these low pressure pulses can be calculated to give good smooth power- the length and diameter of the header pipes are calculated...not just made to fit where they will..... like on a "chopper tv show"

if the exhaust gasses slow, eddy and even reverse course this can result in less air in the cylinder- less power----- maybe you only get 750cc of air into that 844cc cylinder

a "too large" exhaust almost always results in poor low rpm operation- you can see this on the street, that "tuner" honda driven by the 19 year old up the street- notice how he has to rev the crap out of it to get moving from a stop? the same will be seen for harley owners with too large or true dual type exhaust systems.

some don't care they value noise over power.

the above comments on a tuner could be partly correct however the tuner will only work as well as the setting entered- and the owners above are each just guessing- with guesses 180ş apart.
It is completely possible that a given set up can be too rich at one rpm and too lean at another- so all opinions can be partly right, like a broken clock is right twice a day.


if you prime consideration is smooth low end power- I would leave the bike as is.

2nd choice ( and I am cheep) would be remove the cat from the header and use stock mufflers - about $150. This will be a slightly louder and some of the riders here are happy with that result

3rd choice would be catted header and a tunable muffler...I use supertrapps ( and also the screaming eagle fatshots- modified). supertrapps are expensive, but have a 2/1 I've been using for 26 years- so....


for these last 2 choices you likely need a tuner- and how well that works depends on the settings entered by you, or a tech, or some guy down the phone line...
tuners are much improved the past couple of years- but my wallet likes the nightrider.com xieds- essentially they add about 8% more fuel in a linear manner at all rpms ranges- except for wide open throttle and when the bike is cold.




Mike

 

Confused by all of the suggestion for a tuner. It always been suggested that you don't need a tuner if all you're doing is adding slip-ons, right? Stock everything back to the mufflers and then slip-ons. Would I get better results with the Screaming Eagle mufflers?